Carbonaceous materials with nanoscopic structures have been studied extensively and used widely because of their low specific gravity, good electrical conductivity, high surface area, ability to be readily surface-modified, as well as the feasibility of large-scale production. Examples of these materials are carbon black, carbon nanotubes, carbon nanofibers, ordered mesoporous carbons, and so on. Porous colloid imprinted carbon (CIC) powders have also been prepared with a narrow pore size distribution and three-dimensionally connected nanopores, verified by nitrogen adsorption isotherms and three-dimensional transmission electron microscopy (3D-TEM) [1, 2]. These nanomaterials are being used in many applications, such as electrochemical devices, including batteries, capacitors, and fuel cells.
However, most of these carbon materials are available only in powder form, which limits their applications. Variation in the orientation or alignment of the individual nanoporous carbon particles may affect mass transport through the nanopores and also make product properties irreproducible. In addition, use of carbon powders has associated health concerns, since particulates are known to be an increasing problem.
In some cases, carbon powders can be obtained already bound together with a polymer. For example, Pt-loaded nanoporous carbon can be bound with a polymer to serve as the catalyst layer in polymer electrolyte membrane fuel cells (PEMFCs). However, these polymeric binders may negatively affect the conductivity or mass transfer through the carbon powders or may contaminate them, thus lowering their performance. To handle this problem, electrically conducting polymers (e.g., polyaniline) are used as a binder in supercapacitors to improve the conductivity between carbon particles. However, the polymeric phase may narrow the pathways for electrolyte ions, which is expected to decrease the charge/discharge rate of the capacitors.
In the past decade, a number of techniques have been developed to fabricate nanoporous carbonaceous materials in bulk form, e.g., carbon gels or monoliths, carbon films [3-6], carbon tapes [7], carbon cloth, etc. Of these, nanoporous carbon films (NCFs) are very promising for various applications, including applications as electrodes, adsorbents, catalysts, separation materials, and sensors. NCFs can be prepared via hard-template or soft-template methods, filtration, pyrolysis of polymer precursors, chemical or physical vapor deposition, and other chemical and physical methods [6, 8-14], These techniques can provide NCFs with excellent properties, but they also face one or more of the following problems: high cost of raw materials, complicated/tedious or time-consuming preparation process, low mechanical strength, low electrical conductivity, low porosity, non-continuous nano-pores, uncontrolled orientation of the pores, and challenges with mass production.